# How do you express 9isqrt(-36) as a product of a real number and i?

$9 i \sqrt{- 36} = - 54$
First of all, we need to get rid of the square root: since $\sqrt{a \cdot b} = \sqrt{a} \sqrt{b}$, we have that $\sqrt{- 36} = \sqrt{- 1} \sqrt{36} = i \cdot 6$.
$9 i \cdot 6 i = 54 {i}^{2} = - 54$, so it was actually a real number, and you can't write it as a product of a real number and i